Treatment of hydrocarbons



Feb. 12, 1935. 5 P, BURKE r AL N 1,991,344

TREATMENT OF HYDROCARBONS Filed Jan. 23, 1929 2 Sfieets-Sheet 1 7 52METER commas R" I f 26 44 ha l l--J6HEATJ6{ A METE ABSORBER I INVENTORSCQHARLEs E FRYL NG bTEFHEN P- SUI-(IRE.

Patented Feb. 12, 1935 1,991,344 max m-2m or nr'naocaanous Stephen P.Burke, Plainfield, and Charles F. mling, Metuchen, N. J., assignors toDoherty Research Company, New York, N. Y., a corporation of DelawareApplication January 2:, 1929, Serial No. 334,589

13 Claims.

This-invention relates to the transformation of hydrocarbons by partialoxidation into useful hydrocarbon-oxygen compounds. 4

Methods heretofore suggested for effecting the 5 partial oxidationtreatment of a mixture of a hydrocarbon and air to produce valuableintermediate oxidation products (such as alcohols, aldehydes, acids andketones) have usually contemplated contacting a mixture of thehydrocarbon and air at an elevated temperature with a solid metal ormetal oxide contact catalyst capable of accelerating heterogeneous(surface) oxidation of dehydrogenation reactions. So far as is knownnone of these proposed methods have 3 produced altogether satisfactoryyields of intermediate (as distinguished from complete) combustionproducts.

The primary object of the present invention is to provide a process foreifectingthe partial oxi- D dation of hydrocarbons with oxygen or airwhereby satisfactory yields of hydrocarbon-oxygen compounds areobtainable.

A more specific object of the invention is to provide a process foreffecting the partial oxida- 5 tion of hydrocarbons whereby the majorpart of the oxidizing agent is utilized in forming partial (asdistinguished from complete) combustion products. I One of the principalfeatures of the process hereindescribed is that it contemplates carryingout the partial oxidation reactions in' the absence of solid contactcatalysts for heterogeneous (surface) reactions of the type abovereferred to. In other words the process as carried out embodiesprinciples of homogeneous (gasor vaporphase) oxidation and utilizes areaction vessel having its walls, and other parts in contact with thereaction mixture, preferably constructed of an inert substance havingsubstantially no apparent surface catalytic'effect on oxidation ordehydrogenation reactions.

vWith these and other objects and features in view the inventionconsists in the method of producing hydrocarbon-oxygencompounds bypartial oxidation of hydrocarbons which is hereinafterdescribed and moreparticularly defined in the claims.

Various features of the invention are illus- .0 trated in theaccompanying drawings, in which: Fig. 1 is a flow sheet of the principalsteps of the process, illustrating diagrammatically a cross v sectionalplan view of a. preferred type of reaction chamber.

Fig. 2 is an enlarged view in vertical cross gas gasoline therefrom. Ifthe gas is known to section of a reaction chamber of the type shown inFig. 1. N

Fig. 3 is a curve showing the rather wide temperature range within whichpartial oxidation of several of the lighter hydrocarbons of the parafllnseries may be carried out.

Fig. 4 is a curve illustrating the narrow temperature range within whichthe reactionmay go to completion once it has been initiated.

Fig. 5 is a curve showing the effect of variation in pressure on thetemperature at which partial oxidation takes place.

The improved process may be carried out according to the planillustrated in the accompanying flow sheet substantially as follows:

A hydrocarbon to be treated, (for the purpose of this illustrationconsidered as a natural gas of relatively high calorific valuecontaining in addition'to methane smaller amounts of higherhydrocarbons, including ethane, propane and butane) is drawn from a main10 and passed through a meter 12 for the purpose of determining thevolume rate of flow. From meter 12 the gas is passed through acompressor 14 wherein it is compressed to a suitable, normallyrelatively high pressure. After being thus compressed the gas may beconducted through an absorber or equivalent apparatus 16 for the purposeof separating liquefiable constituents such as natural contain only verysmall amounts of natural gas gasoline hydrocarbons, or if their removalis not desired, it may be by-passed around the absorber 16 through avalved line 18. The measured portion of gas which is to be treated isnext conducted through a valve 20 into a manifold 22 and any part of thegas which it is not desired to treat is passed back through a valve 24to the main line 10. A part, or all, of the gas delivered to themanifold 22 is passed into a valved line 26 and thence either throughthe tubes or coils of a main heat interchanger 28 and an auxiliary heatinterchanger 30, or around the interchanger through a. valved by-pass32. From the delivery side of interchanger 30 the gas is deliveredthrough a continuation of pipe 26 to an air-gas mixing nozzle 34 mountedin an inlet-chamber 36 of a high pressure oxidation vessel 38. Ameasured volume of air (or oxygen or other gaseous oxidizing medium),under a pressure slightly higher than that on the gas, is intimatelyadmixed with the gas at 34 by jetting the air from a yalve controlledair supply line 40. Air is delivered to the line 40 either throughinterchangers 28 and 30.

or around the interchan'gers through a by-pass 42. The air is conductedto the interchangers by a pipe 44 which in turn receives a continuousthroat mixers and the like if desired) is mounted at the inlet 36 ofvessel 38 and functions to effect thorough intermingling of thehydrocarbon and the air or other' oxidizing medium which make up thereaction mixture. In the reaction zone of the vessel 38 the oxygen ofthe reaction mixture enters into chemical combination with one or moreof the hydrocarbon constituents of the natural gas under conditions oftemperature, pressure and the like which experience has shown to be bestsuited for effecting homogeneous partial oxidation to form intermediatehydrocarbon-oxygen compounds (in preference to complete oxidationproducts of the carbon-oxygen and hydrogen-oxygen type). The hotprodnets of the reaction which takes place in vessel 38 exit from thevessel, still under pressure, through a. pipe 52 and are passed directlyinto and through a hot gas chamber 54 of the interchanger 28. Chamber 54lies between flue sheets 56 and surrounds the flues of the interchanger.

changers 38 and 30 into separate passages to air and gas passing to thereaction vessel.

From chamber 54 the products of reaction pass by a line 60 into acondenser 62 and from thence into an absorber 64, wherein anyintermediate oxidation products formed during the treatment in thereaction chamber are liquefied and separated from the gaseous residue.Refrigeration is normally used in cooling the condenser 62 and absorber64. The treated gaseous residue is passed into a pipe 66 from which itis either recycled through manifold 22 for treatment in a similar mannerwith a fresh portion of oxidizing gas in the same orv in anotherreaction vessel 38, or else such gaseous residue may be conductedthrough a valve 68 into a manifold 70 and thence back to the gasdistributing main 10 through a valve 72. If desired the gaseous residueof the first stage of the treatment may be conducted by extension '74 ofmanifold 70 into and through another set of apparatus units 38, 62 and84, (not shown) the treatment in such second stage and in eachsubsequent stage being preferably carried out after admixture ofrelatively smaller volumes of oxygen-bearing gas with the hydrocarbon tobe treated.

The preferred design of reaction vessel (see Fig.

' 2) embodies a pressure-resistant, air-tight casing 76 having itsinterior divided by heat-conductant partitions (comprising flue sheets78 and flues or tubes 80) into relatively gas-tight, pressure-resistantpassages for the reaction mixture and products of the reaction, and intoa chamber 82 surrounding the tubes in which a fluid cooling ortemperature control medium is normally circulated. The oxidationreactions take place in tubes 80, and communicating with these tubes atopposite ends thereof are inlet and outlet chambers 36 and 84 forconducting the reaction mixture and products of reaction, respectively,to and within the contemplation of the invention.

away from the reaction zone. A partition 86 extends longitudinallybetween the flue sheets '78 and divides chamber 82 into two sections 87and 88 (see Fig. 1). ing media are circulated at a controlled rate andunder a controlled pressure through the sections 87 and 88 throughoutthe period of the treatment for the purpose of maintaining careful andLiquid or gaseous heat absorb-' accurate control of temperatures in thereaction tubes 80 by a rapid removal (at a controlled rate) of excessheat liberated by the exothermic reactions in the tubes 80 in the formof sensible heat in the fluid circulating medium. The fluid temperaturecontrol medium which is maintained in circulation in'section 87 ofchamber 82 throughout the period. of the reaction enters chamber 82through a valved connection 90, and leaves through a valved connection92. Similarly the fluidflwhich is maintained in circulation in section88 enters this section through a line 91 and leaves through a line 93.Lines 90, 91, 92 and 93 have been shown (Fig. 1) in closed circuit witha' hot fluid chamber 94 (formed between flue sheets 56 and surroundingthe flues or coils of the heat exchanger 30), as well as with pumps 96.The closed circuit thus provided is utilized for cooling and circulatingat a controlled rate any fluid which may be employed as a-temperaturecontrol medium in vessel 38.

A valved pipe connection 98 is provided between .the pipe and the pipe26 on the inlet side of the valve 100 therein. Likewise a valvedconnection 102 connects pipe 92 with the discharge side of valve 100. Byvirtue of these connections gas on its way to the reaction vessel may beused as the temperature control medium for circulatic'n around thereaction zones of tubes 80, if desired. A pipe 104 similarly connectsline 91 with pipe 40 and may be used to conduct at from pipe 40 into thetop of section 88; while a pipe 106 is likewise provided to conduct air,back from line 93 into pipe 40 on the discharge side of the valve 108.The purpose of partition 86 is similar to that of partition 58 in theinterchangers 28 and 30, namely to prevent the intermingling of thehydrocarbon and the oxygen-supplying components, respectively, of thereaction mixture during periods in which such components are employed astemperature controlling media in sections 8'! and 88 of the reactionvessel. The small or section 88 of chamber 82 is normally used as an aircirculating chamber because of the fact that the reaction mixturenormally contains less air than gas.

The partial oxidation reactions leading to formation of aldehydes andalcohols and similar intermediate oxidation products in accordance withthe present process are believed to be chiefly homogeneous in character,at least under the conditions of operation outlined herein, andaccordingly the use in the reaction zone of known metal and metalcompound contact catalysts such as platinum or vanadium oxide ispreferably avoid- -ed. However, it is not desired to limit the presentprocess to any particular theory as to the homogeneous character of thereaction or otherwise, and the employment of gas or vapor phasecatalysts andthe principles of auto-catalysis are If the process is notone of homogeneous oxidation it exhibits most of the characteristics ofhomogeneous oxidation reactions, and it has been noticed that in generalthe presence of any of the well known solid contact catalysts in thereaction zone will decrease the yield of intermediate products ascompared with the yields obtained in the absence of such catalysts. Forthis reason the expression homogeneous partial oxidation reaction" hasbeen used in the description and claims as, a generic term to deflne areaction which takes place with substantially equal velocity (and in theabsence of contact catalysts) throughout all sections of the reactionzone; as

oxidation of hydrocarbons, are considered to function primarily toactivate surface or heterogeneous reactions, the principal (andsometimes the only recoverable) products of which are completecombustion products, namely carbon oxides and water. For this reason andin order to avoid any difficulties in temperature control which wouldresult from the development of hot spots (that is local highly energizedreaction centers) in the reaction tube, each tube or flue 80 ispreferably constructed of, or lined with, a relatively highly heatconductant non-catalyst material such as aluminum, while a cooling fluidof accurately controlled temperature is rapidly circulated at acontrolled rate therearound. Moreover each of the tubes 80 of thereaction vessel is preferably of small cross section and has arelatively large heat transfer surface per unit of cross sectional area.Thus even in. a commercial size apparatus the diameter of the reactiontubes is normally limited to a maximum of one inch, and in cases whereit is necessary to employ reaction tubes of larger diameter than oneinch,

such larger tubes are normally filled with a granulated inert heatconductant material such as aluminum tumings.

The temperature of initial combustion of a hydrocarbon such as propaneis higher in the presence of aluminum than it is in the presence of suchmetals as platinum and copper. As distinguished from most metals,however, aluminum is 'not a catalyst for complete combustion ofhydrocarbons and consequently the use of alumi-j num favors a high yieldof aldehydes obtained by partial oxidation of hydrocarbons by preventing or reducing the substantial loss of hydrocarbons by heterogeneousreactions. Stainless steel, iron and prex glass have been satisfactorilysubstituted for aluminum in constructing the reaction tubes or theirlinings. Materials of this type are known to be substantially inert sofar as their power to activate surface oxidation reactions is concerned.The use of-a flller such as aluminum turnings in the reaction tubeserves to inhibit; or to at least partially inhibit, the formation of ofhot spots, probably because the high thermal conductivity of thismaterial serves to rapidly dissipate or transfer any excess heatdeveloped in the reaction zone, to the fluid cooling medium surroundingthe tubes. It is recognized that an oxide film may form on the surfaceof aluminum thus used, but if such is the casethe results show that theeffect of the oxide on the process is substantially the same asthat ofthe metal.

In starting the operation of the process the reaction vessel is broughtup to the necessary reaction temperature either by some external heatingmeans, such as electrical resistance heating elements (not shown). or bycombustion of a small part of the hydrocarbon which is to be 1 reactionvessel.

treated. When very low concentrations of oxygenareusedinmakingupthereactionmixtureit may sometimes be foundadvantageous or necessary to use small amoimts' of contact catalysts inthe reaction chamber in order, by reason of the complete combustionreaction thereby promoted, to make'the reaction self-sustaining in thematter of maintenance of the necessary reaction temperature. Usuallyhowever, theuse of such contact catalysts is neither necesary nordesirable.

While the initial stage of reaction treatment is preferablyhomogeneousjincharacter, one or more subsequent stages of treatment maybe carried on in the presence of contact catalysts. For example, wherethe reaction mixture formed in the initial homogeneous reaction containsacids,

aldehydes', alcohols and hydrogen, the passage of this mixture in asubsequent reaction stage over a catalyst such as silver or platinumwill cause the hydrogenation of aldehydes and acids to alcohols, thusgiving a simpler and more de-' sirable final product. Obviously othercatalysts can be employed with a similar object in view.

Following is a brief description of an application of the presentprocess to the partial oxidation of commercial propane:-A measuredvolume of this gas is vaporized under a superatmospheric pressure ofabout 400 lbs. per square inch and is admixed with about 30% of itsvolume of air, under a slightly higher pressure, to

make up the reaction mixture. The gas and air components of the reactionmixture are separately preheated to about 250Zi00 CL, and the reactionmixture is formed by thorough intermingling of its components just atthe entrance of the The reaction mixture thus formed is passed into andthrough a number of open aluminum lined steel reaction tubes of aboutone fourth inch diameter, the temperature of such tubes, or rather ofthe fused nitrate bath in which the tubes are immersed, being maintaineduniform at about 350 C. It will be understood that the averagetemperature inside the open reaction tube is diflicult to measure but itmay be at least 25 C. higher than the temperature of the surroundingbath. The rate of passage of such that the time of sojourn of any unitvolume thereof in the reaction tube is ordinarily less than one second.It is desirable to hold the mixture of hydrocarbons and oxygen-supplyinggas not higher than 50 C. above the temperature at which the partialoxidation reaction is initiated in such mixture. On leaving the reactionzone the prod-.

ucts of the reaction are immediately and rapidly cooled and part oftheir sensible heat is recovered by passing them through a heatinterchanger in heat transferring relationship with the gas and airpassing to the reaction vessel. Any condensible liquidhydrocarbon-oxygen compounds formed during the course of the reactionare separated from the gaseous residue in suitable condensing andabsorber equipment. The entire operation, including the reaction andseparation of the gaseous and liqueflable products of the reaction, ispreferably carried out under the specified pressure. Among the productsof the treatment are water, small amounts of substances containingactive oxygen such as organic peroxides and materials derived fromorganic peroxides, methanol, acetaldehyde, formaldehyde andotheralcohols, aldehydes, ketones, acetals and acids.

The liquid reaction product obtained by partial the reaction mixturethrough the tubes is I oxidation of commercial propane in accordancewith the treatment described consists largely of compounds the moleculesof which all contain less than three carbon atoms. However there mayalso be present in this product small amounts of compounds the moleculesof which contain three or more carbon atoms. In general the use ofreaction mixtures of low initial oxygen concentration and themaintenance of high pressures, high rates of flow and low temperaturesin the reaction zone are all conducive to production of a liquid productof. high molecular weight and low water content. The average molecularweight of a liquid product obtained by partial oxidation of propane inaccordance with the treatment above specified is from to 35 as comparedwith 18 for water. The gaseous residue of the treatment contains nouncombined oxygen (if the reaction is properly carried out) and may beused as a fuel or may be admixed with another portion of air andsubjected to a similar treatment in a second stage of partial oxidation.Complete utilization of the free oxygen contained in the originalreaction mixture used in each stage of the treatment is preferredbecause, for one reason, it is known that both the liquid and gaseousproducts of the reaction are strongly corrosive in case there is freeoxygen associated therewith.

It should be mentioned that in certain cases it may be desirable toseparate from the gaseous reaction residue, its content of unacted uponpropane. This can readily be accomplished by proper cooling of thegaseous residue preferably after the hydrocarbon-oxygen products havebeen removed.

In treating a natural gas containing large proportions of methane underthe conditions of pressure and the like just specified, it has beenfound bestto employ a reaction temperature in the neighborhood of425-450 C. In treating butane, on the other hand, the reactiontemperature may be dropped to about 325 C. The optimum reactiontemperature for treating other hydrocarbons of the paraffin series underthe conditions of pressure and the like stated in the example may beinterpolated from the values given (see Fig. 3). The most advantageoustemperature range at which to carry out the partial oxidation of propaneis fairly wide (depending upon pressure, size of reaction vessel, andother conditions under which the reaction takes place). This rangeincludes temperatures of 300 C. to about 450 C. A correspondingtemperature range has been 'aund for treating the other hydrocarbons ofthis coup, as the foregoing data indicates. The optimum treatingtemperature increases proportionately as the number of carbon atoms inthe hydrocarbon molecule decreases, and vice versa. The most desirabletemperature is usually one approaching closely the temperature ofinitial reaction of the reaction mixture at the pressure employed, forthe reason that if the temperature is carried much above thetemperatureat which reaction commences, side reactions occur, the ultimate productsof which are carbon oxides and water. i

The minimum temperature below which no partial oxidation reaction takesplace is in general considerably higher than the temperature at whichcomplete combustion reactions are activated in the presence of suchheterogeneous reaction catalysts as platinum or copper.

It is a feature of this invention that the process described is verysensitive to changes of temperature. Thus, as the process is ordinarilyconthe temperature of initial reaction, the increase in reactionvelocity is so great that a temperature difference of less than 3 C.often separates the condition of the system in which there is small,barely detectable reaction, and the condition in which the reactionmixture loses all of its free oxygen with the formation of theintermediate 4 compounds previously mentioned. (See Fig. 4.)

It has been found to be difficult to measure the temperature of initialreaction, but it is not difficult to obtain an accurate measurement ofthe temperature of half reaction, which is the temperature at which halfof the oxygen of the initial reaction mixture has entered intocombination reactions. This temperature has been found to depend uponthe following conditionsz-nature of the hydrocarbon or composition ofthe hydrocarbon gas if a mixture of hydrocarbon is being treated,initial concentration of air or oxygen used, rate of flow thru reactionzone, diameter and length of reaction cylinder, i. e., design of theapparatus employed, the presence of certain substances which can act asdetonators, catalysts or inhibitors to the reaction, and the pressureemployed.

Thus it has been found that the temperature of half reaction of 70%propane% air mixtures, in the absence of any known catalyst, detonatoror inhibitor, all of the experiments being conducted in the sameapparatus and the thruput of reaction mixture being held the same foreach determination, is lowered by an increase in pres sure substantiallyin accordance wth the following equation:--

*(T being expressed in degrees Kelvin and P in' pounds per square inch).

In treating paraffin hydrocarbons of the ethane to octane range by thepresent process, pressures ranging from 100 lbs. 1750.1bs. per squareinch have been employed. Apparently the most satisfactory andpracticable pressures are those in the neighborhood of 300 to 500 lbs.per square inch. The efliciency of the treatment, or in other words, thepercentage of the oxygen content of the initial reaction mixture whichis obtained in the form of liquid organic hydrocarbon-oxygen products,increases with an increase in pressure up to about 500 lbs. per squareinch. The increase is not so marked at pressures above this point. Thusthe liquid product obtained by subjecting commercial propane to partaloxidation at atmospheric pressure consists chiefly of water (as much as90%) and small amounts of formaldehyde; whereas the treatment ofcommercial propane at 400 lbs. per square inch in accordance with theexample stated above normally yields a product containing less than 30%water and more than 70% of liquid hydrocarbon-oxygen products. In otherwords an increase in pressure from atmospheric to 400 lbs. per squareinch, with a corresponding drop in reaction temperatures, results in acorresponding increase in. the proportion of oxygen content of theinitial reaction mixture which is converted into hydrocarbon-oxygencompounds as distinguished from products of complete combustion. As thepresure under which the reaction is carried out increases the proportionof the initial per square inch to.

continue to increase with an increase in pressure.

If the rate of flow and composition of the reaction mixture is heldconstant the acidity of the liquid product also increases with anincrease in pressure. In treatingpropane under pressures between 300 and400 lbs. per square inch the reaction is unnoticeable at temperaturesbelow 280 C. However in accord with the equation shown above thereaction is suddenly completed within the range of 300 to 400 C. (SeeFig. 5.)

In the oxidation of propane temperatures above about 400 to 440 C., areunnecessarily high and result in complete oxidation reactions andthermal decomposition of at least part of the intermediate oxidationproducts formed. The optimum reaction temperature for propane under suchpressures andin the absence of. a catalyst appears to be about 350 C.The same may be said for other hydrocarbons of the parailin series,except that the optimum temperature is displaced upwardly or downwardlydepending on the decrease or increase, respectively, in the number ofcarbon.

' atoms in the hydrocarbon molecule.

The temperature of initial reactionofa hydrocarbon-air mixture increasesas the oxygen concentration of the reaction mixture increases. The mostsatisfactory products and the most efficient conversion of oxygen toproduct usually occurs when using a reaction mixture of lowinitial'oxygen concentration, i. e., below 50% air by volume. Howeverreaction mixtures having a much higher initial oxygen concentration canbe satisfactorily oxidized if it is practicable to use sufficientlysmall sized reaction tubes. It has been observed that the initialreaction temperature of a hydrocarbon-pure-oxygen mixture is lower thanthat of a hydrocarbon-air mixture of thesame oxygen concentration. Inother words for any given oxygen concentration the reaction takes placeat a lower temperature when pure oxygen is substituted for air in makingup the reaction mixture. In treating a propane-pureoxygen mixture thetemperature of half reaction was found to increase with an increase inthe initial oxygen concentration up to a temperature of 342.5 C. at anoxygen concentration of 5%. With increase of oxygen concentration above5% the temperature of half reaction remains con-. stant. The lowesttemperature at which any oxidation with air took place under similar conditions of pressure and the like was 325 C., whereas with oxygen it wasbelow 300 C. The amount of initial oxygen in the reaction mixture whichis wasted by combination to fonn oxides of carbon and water increases asthe temperature at which the reaction is conducted increases.

The temperature of half reaction of a hydrocarbon oxygen mixturecontaining two or more hydrocarbons, one of which is less readilyconverted than the other by the process into intermediate oxidationproducts, increases as the proportion of such less readily oxidizablehydrocarbon in the reaction mixture increases. Thus it was found thatthe temperature of half reaction of a reaction mixture comprising 49.7%propane, 21% methane and 29.3% air was 353.5 0. when treated in a 1 i.(1. steel reaction tube 11 feet long under a pressure of 750 pounds/sq.in,

with a slow rate of flow, namely 7.76 cu. ft./hour. The temperature ofhalf reaction of a propaneair mixture containing 70.6% propane was 345.50., under similar reaction conditions. The liquid oxidation product ofthe propane-air mixture was of slightly higher molecular weight, andtheC0 content of the gaseous residuewas slightly lower than thecorresponding products of treatment of the propane-methane-air mixture.It appears,

therefore, that the methane component. of the propane-methane-airmixture acts merely as a diluent, being comparable with the nitrogen ofthe air used in this respect.

It has been found that at any given pressure and temperature themolecular weight of the liquid hydrocarbon-oxygen product of thetreatment of an original hydrocarbon-air mixture decreases with increaseof initial oxygen concentration. For hydrocarbon-air mixtures having an'initial oxygen concentration much above 10% it has been found that thevalue of the liquid products drops of! rapidly with further increase ininitial oxygen concentration. The use of hydrocarbon-pure oxygenmixtures in place of hydrocarbon-air mixtures of equal oxygen contentresults in slightly better yield of higher molecular weight products.The liquid product obtained by treating a propane-pure-oxygen mixtureunder substantially the conditions of pressure and the'like specifiedabove had a water content of about 15% and a molecular weight of about33. The liquid product obtained by treating a propane-air reactionmixture of corresponding oxygen concentration under the same conditionscontained about 30% water and had a molecular weight of 29. When usinghydrocarbon-pureoxygen mixtures the eiliciency of oxygen conversion ofthe process decreases less rapidly with an increase of oxygenconcentration than when using hydrocarbon-air mixture; an efllciencyofas high 'as 66% conversion of all initial oxygen to hydrocarbon-oxygenproduct having been obtained.

Several runs with a commercial propane-air mixture under uniformconditions of pressure and oxygen concentration have shown a gradualincrease in reaction temperature over a range of about 40 C. with anincrease in rate of flow from 6 to 36 cubic feet per hour. Thus astraight line relationship exists between the temperature ofhalf-reaction and therate of flow of the reaction mixture through thereaction zone, at least in reaction tubes of small cross section. Theyield of product increases as the rate of flow increases. The results ofa series of runs made in a inch reaction "tube twelve feet long with apropane-air mixture containing 30% air at 750 lbs. per square inchpressure, to determine the effects of varying the rate of now on thecharacter of the product, indicatedthat the acidity of the liquidproduct increased with an increase in rate of flow up to about 16 cu.ft. per hour and then decreased with a further increase in flow, thusshowing a maximum acidity with a turbulent flow rate of 16 cunft. perhour. The results of other runs have shown that with constant pressureand rate of flow the acidity of the liquid product ofthe treatmentdecreases as homogeneous character of these partial oxidation reactions,at least so far as treatment of the low boiling paraflin hydrocarbon isconcerned, satisfactory temperature control appears to be best insuredby the use either of larger sized reaction tubes filled with granulatedcatalytically inert material or of open unobstructed tubes of small,almost capillary, size, preferably constructwas found to be the initialreaction temperature for a propane-air mixture containing 30% air passedat a rate of 4 cu. ft. per hr. under 750 lbs. per square inch pressurethrough a 1; inch inside diameter reaction tube 12 ft. long, whereas thecorresponding initial reaction temperature of the same mixture in a 4inch inside diameter tube of the same material under like conditions was307 C.

The process of the invention has particular utility in producingformaldehyde, methanol and acetaldehyde from paraflln hydrocarbons ofthe ethane to octane range. It will be understood, however, that theinvention is not limited to the production of any specifichydrocarbon-oxygen compound or to the partial oxidation treatment of anyspecific type of hydrocarbon. Thus the process has been applied to thetreatment of methane and also to the treatment of unsaturatedhydrocarbons, including ethylene and other oleflns.

The invention having been thus described, what is claimed as new is:

1. The process of producing hydrocarbon-oxygen compounds comprisingheating a mixture containing a fluid aliphatic hydrocarbon and-less than10% by volume of free oxygen in theform of an oxidizing fluid atsuperatmospheric 'prese sure above per sq. in., anda temperature withinthe range of from 200 to 500 C., in a narrow, unobstructed reactionzone, thereby effecting a homogeneous partial oxidation reaction and theproduction of a fluid reaction mixture containing the saidhydrocarbon-oxygen com pounds and hydrogen, and reacting the fluidreaction mixture containing the hydrocarbon-oxygen compounds whilecontacting it with a reducing catalyst adapted to convert to alcoholsthe aldehydes and acids present in the said mixture ofhydrocarbon-oxygen compounds.

2. The process of producing intermediate hydrocarbon-oxygen compoundscomprising reactin: a mixture containing an aliphatic hydrocarbon withnot more than 10% by volume of oxygen in the form of an oxygen-supplyinggas, within an unobstructed reaction zone of narrow transverse sectionfree from solid contact catalysts and maintained at a temperature withinthe range of 200 to 500 0., and under a pressure within the range from200 to 1750 poundsper square inch and passing. the said reaction mixturethrough the reaction zone at such rate that it is exposed to the hightemperature there- 3. The process of producing intermediatehydrocarbon-oxidation products which comprises reacting a gaseousaliphatic hydrocarbon with less than one-tenth of its volume of freeoxygen at a temperature between 200 and 500 0., and at a pressure above100p0unds per square inch, within an unobstructed aluminum-linedreaction zone, and quickly removing the resultant reaction products fromthe said zone after exposure to the high temperature therein for aperiod of not more than one second.

4. The process of producing intermediate hydrocarbon-oxygen productscomprising rapidly flowing an intimate mixture of a gaseous aliphatichydrocarbon and oxygen through an elongated unobstructed reaction zoneof less than one inch transverse thickness while out of contact with anysolid contact catalyst, the said zone being maintained at a temperaturein the range of 200 to 500 C., and at a corresponding superatmosphericpressure above 100 pounds per square inch, adapted to initiate andmaintain homogeneous partial oxidation reactions almost exclusively,maintaining a substantially uniform temperature within the reactionzone, and rapidly dissipating any excess heat developed therein.

5. The process of producing intermediate hydrocarbon-oxidation productscomprising quickly reacting a fluid aliphatic hydrocarbon with not morethan 10% of its volume of oxygen in the form of an oxygen-supplying gasat a pressure within the range from 200 to 1750 pounds persquare inchand at a corresponding temperature in the range of 200 to 500 C. butwhich is not more than 50 (7., above the initial reaction temperature ofthe said mixture of hydrocarbon and oxygen-supplying gas.

6. The process 01' producing intermediate hydrocarbon-oxidation productscomprising separately preheating a gaseous aliphatic hydrocarbon and anoxygen-supplying gas, intimately mixing the said preheated fluids andflowing the mixture in a thin stream through unobstructed reaction zonemaintained at a temperature within the range of 200 to 500 C., and undersuperatmospheric pressure, the said reaction zone being free jrom solidcontact catalysts and being immersed in a heat-transferring bathmaintained at a temperature approximately that of the reacting mixture,thereby inhibiting heterogeneous oxidation reactions and promotinghomogeneous partial oxidation reactions, the hydrocarbon and oxygenrespectively being preheated to a temperature within 100 C. of thetemperature maintained in the said reaction zone.

7. In the manufacture of hydrocarbon oxygen compounds the stepscomprising passing a reaction mixture containing propane and oxygen inthe proportions of substantially 10 to 1 by vollume through a reactionzone maintained at a temperature of 325 to 400 C. and under a pressureexceeding 100 lbs. per square inch, and from which solid contactcatalysts for oxidation reactions are excluded.

8. In the manufacture of hydrocarbon-oxygen compounds, the stepscomprising treating a hydrocarbon body containing propane, admixed withless than 50% of its volume of air, to homogeneous partial oxidationunder a pressure ranging from 300 to 500 lb. per square inch and at atemperature of about 350 0., the period of exposure oi thehydrocarbon-air mixture to the said temperature being less than onesecond.

9. In the manufacture of hydrocarbon-omen compounds the steps comprisingpassing a reaction. mixture containing an aliphatic hydrocarbon havingless than 8-carbon atoms in its molecule and less than 50% of its volumeof air, in a plurality o1 finely divided streams each less than one inchin cross section, through a reaction zone from which solid contactcatalysts are excluded and which is maintained at a temperature rangingirom'200 to 500 C. and under a pressure exceeding 300 lbs. per squareinch.

10. A method of converting an aliphatic hydrocarbon having a highermolecular weight than methane into intermediate oxidation products,

which comprises treating the said hydrocarbon in a small unobstructedreaction zone with less than .ten'per cent of its volume of oxygen whilecontinuously maintaining the mixture under a superatmospheric pressurewithin the range of from 200 to 1750 pounds per square inch and at atemperature within the range oi'irom 200 to 11. The method ofselectively converting the propane content of a hydrocarbon mixturecontaining methane and propane into an intermediate oxidation productcomprising, treating said mixture to partial oxidation with oxygen -at atemperature of about 350 C. and under a pres-.

sure exceeding 100 lbs. per square inch in the absence of a solidcontact catalyst for oxidation reactions.

12. The process of producing intermediate hydrocarbon-oxidationcompounds which comprises forming a mixture of a fluid aliphatichydrocarbon and an oxygen-supplying gas, and flowing the said mixtureinto and through an elongated unobstructed reactionzone of between 1*inch and one inch in transverse thickness, while maintaining thereon apressure of over 100 pounds per square inch, the said reaction zonebeing maintained at a temperature within the range of 200 to 500 C., andseparately preheating the hydrocarbon and the oxygen-supplying gas to atemperature within 100 C. of the temperature maintained in the saidreaction zone prior to intermixture thereof.

13. The process of producing hydrocarbon-ox- Lidation products whichcomprises subjecting a mixture or an oxygen-supplying gas and analiphatic hydrocarbon having not more than 8 carbon atoms in itsmolecule to a pressureof from 200 to 1750 pounds per square inch and toa temperature of from 200 to 500 C. in the absence of solid contactcatalysts, thereby initiating and maintaining a homogeneous gas phasepar!- tial oxidation reaction and producing the saidhydrocarbon-oxidation products, and recovering the latter.

STEPHEN P. BURKE.

CHARLES F. FRYIJNG.

